package cn.woblog.recyclerviewsample.divider;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.LayoutManager;
import android.support.v7.widget.RecyclerView.State;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.View;
import cn.woblog.recyclerviewsample.R;

/**
 * Created by renpingqing on 17/4/6.
 */

public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {

  private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
  private Drawable mDivider;

  public DividerGridItemDecoration(Context context) {
    final TypedArray a = context.obtainStyledAttributes(ATTRS);
//    mDivider = a.getDrawable(0);
    mDivider = context.getResources().getDrawable(R.drawable.item_divider);
    a.recycle();
  }

  @Override
  public void onDraw(Canvas c, RecyclerView parent, State state) {

    drawHorizontal(c, parent);
    drawVertical(c, parent);

  }

  private int getSpanCount(RecyclerView parent) {
    // 列数
    int spanCount = -1;
    LayoutManager layoutManager = parent.getLayoutManager();
    if (layoutManager instanceof GridLayoutManager) {

      spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
      spanCount = ((StaggeredGridLayoutManager) layoutManager)
          .getSpanCount();
    }
    return spanCount;
  }

  public void drawHorizontal(Canvas c, RecyclerView parent) {
    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
      final View child = parent.getChildAt(i);
      final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
          .getLayoutParams();
      final int left = child.getLeft() - params.leftMargin;
      final int right = child.getRight() + params.rightMargin
          + mDivider.getIntrinsicHeight();
      final int top = child.getBottom() + params.bottomMargin;
      final int bottom = top + mDivider.getIntrinsicHeight();
      mDivider.setBounds(left, top, right, bottom);
      mDivider.draw(c);
    }
  }

  public void drawVertical(Canvas c, RecyclerView parent) {
    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
      final View child = parent.getChildAt(i);

      final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
          .getLayoutParams();
      final int top = child.getTop() - params.topMargin;
      final int bottom = child.getBottom() + params.bottomMargin;
      final int left = child.getRight() + params.rightMargin;
      final int right = left + mDivider.getIntrinsicHeight();

      mDivider.setBounds(left, top, right, bottom);
      mDivider.draw(c);
    }
  }

  private boolean isLastColum(RecyclerView parent, int pos, int spanCount,
      int childCount) {
    LayoutManager layoutManager = parent.getLayoutManager();
    if (layoutManager instanceof GridLayoutManager) {
      if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
      {
        return true;
      }
    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
      int orientation = ((StaggeredGridLayoutManager) layoutManager)
          .getOrientation();
      if (orientation == StaggeredGridLayoutManager.VERTICAL) {
        if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
        {
          return true;
        }
      } else {
        childCount = childCount - childCount % spanCount;
        if (pos >= childCount)// 如果是最后一列，则不需要绘制右边
        {
          return true;
        }
      }
    }
    return false;
  }

  private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,
      int childCount) {
    LayoutManager layoutManager = parent.getLayoutManager();
    if (layoutManager instanceof GridLayoutManager) {
      childCount = childCount - childCount % spanCount;
      if (pos >= childCount)// 如果是最后一行，则不需要绘制底部
      {
        return true;
      }
    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
      int orientation = ((StaggeredGridLayoutManager) layoutManager)
          .getOrientation();
      // StaggeredGridLayoutManager 且纵向滚动
      if (orientation == StaggeredGridLayoutManager.VERTICAL) {
        childCount = childCount - childCount % spanCount;
        // 如果是最后一行，则不需要绘制底部
        if (pos >= childCount) {
          return true;
        }
      } else
      // StaggeredGridLayoutManager 且横向滚动
      {
        // 如果是最后一行，则不需要绘制底部
        if ((pos + 1) % spanCount == 0) {
          return true;
        }
      }
    }
    return false;
  }

  @Override
  public void getItemOffsets(Rect outRect, int itemPosition,
      RecyclerView parent) {
    int spanCount = getSpanCount(parent);
    int childCount = parent.getAdapter().getItemCount();
    if (isLastRaw(parent, itemPosition, spanCount, childCount))// 如果是最后一行，则不需要绘制底部
    {
      outRect.set(0, 0, mDivider.getIntrinsicHeight(), 0);
    } else if (isLastColum(parent, itemPosition, spanCount, childCount))// 如果是最后一列，则不需要绘制右边
    {
      outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
    } else {
      outRect.set(0, 0, mDivider.getIntrinsicHeight(),
          mDivider.getIntrinsicHeight());
    }
  }
}
